全文获取类型
收费全文 | 33102篇 |
免费 | 1622篇 |
国内免费 | 34篇 |
专业分类
电工技术 | 346篇 |
综合类 | 57篇 |
化学工业 | 6941篇 |
金属工艺 | 605篇 |
机械仪表 | 589篇 |
建筑科学 | 1956篇 |
矿业工程 | 78篇 |
能源动力 | 910篇 |
轻工业 | 2901篇 |
水利工程 | 311篇 |
石油天然气 | 197篇 |
武器工业 | 3篇 |
无线电 | 2383篇 |
一般工业技术 | 6062篇 |
冶金工业 | 5735篇 |
原子能技术 | 223篇 |
自动化技术 | 5461篇 |
出版年
2023年 | 257篇 |
2022年 | 297篇 |
2021年 | 700篇 |
2020年 | 508篇 |
2019年 | 598篇 |
2018年 | 736篇 |
2017年 | 711篇 |
2016年 | 920篇 |
2015年 | 831篇 |
2014年 | 1050篇 |
2013年 | 1978篇 |
2012年 | 1702篇 |
2011年 | 2172篇 |
2010年 | 1548篇 |
2009年 | 1493篇 |
2008年 | 1811篇 |
2007年 | 1688篇 |
2006年 | 1496篇 |
2005年 | 1276篇 |
2004年 | 1131篇 |
2003年 | 994篇 |
2002年 | 950篇 |
2001年 | 577篇 |
2000年 | 560篇 |
1999年 | 582篇 |
1998年 | 642篇 |
1997年 | 533篇 |
1996年 | 524篇 |
1995年 | 480篇 |
1994年 | 461篇 |
1993年 | 457篇 |
1992年 | 406篇 |
1991年 | 243篇 |
1990年 | 352篇 |
1989年 | 342篇 |
1988年 | 287篇 |
1987年 | 305篇 |
1986年 | 296篇 |
1985年 | 329篇 |
1984年 | 282篇 |
1983年 | 264篇 |
1982年 | 243篇 |
1981年 | 217篇 |
1980年 | 184篇 |
1979年 | 187篇 |
1978年 | 171篇 |
1977年 | 148篇 |
1976年 | 155篇 |
1975年 | 139篇 |
1974年 | 115篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Quirk Stuart W.; Subramanian Lakshmi; Hoerger Michael 《Canadian Metallurgical Quarterly》2007,116(3):624
The socioemotional functioning of schizophrenic and schizotypic individuals is marked by withdrawal, poor organization, and limited emotional displays. Such behavioral tendencies and lack of social enjoyment in schizotypy could be linked to the relative situational demands or role ambiguity inherent in specific social activities. To determine whether high-schizotypy individuals prefer more clearly role-defined social activities (e.g., visiting relatives) to more ambiguous, novel situations (e.g., going alone to a party), the authors gathered reports from 52 high-schizotypy and 60 low-schizotypy individuals on their enjoyment and frequency of engaging in social situations varying in relative situational demand. Parallel reports were obtained from knowledgeable others. Group × Situational Demand interactions revealed the hypothesized pattern of reduced frequency and enjoyment ratings for ambiguous or novel situations by the high-schizotypy participants in both self and others' reports. Groups were more comparable in their reported frequency and enjoyment of less ambiguous situations. Results suggest the importance of situational demands in the socioemotional experience and behavioral withdrawal in schizotypy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
102.
Leonardo Candela Fuat Akal Henri Avancini Donatella Castelli Luigi Fusco Veronica Guidetti Christoph Langguth Andrea Manzi Pasquale Pagano Heiko Schuldt Manuele Simi Michael Springmann Laura Voicu 《International Journal on Digital Libraries》2007,7(1-2):59-80
This paper introduces DILIGENT, a digital library infrastructure built by integrating digital library and Grid technologies and resources. This infrastructure
allows different communities to dynamically build specialised digital libraries capable to support the entire e-Science knowledge
production and consumption life-cycle by using shared computing, storage, content, and application resources. The paper presents
some of the main software services that implement the DILIGENT system. Moreover, it exemplifies the provided features by presenting how the DILIGENT infrastructure is being exploited in supporting the activity of user communities working in the Earth Science Environmental
sector.
This work is partially funded by the European Commission in the context of the DILIGENT project, under the 2nd call of FP6 IST priority. 相似文献
103.
A recently proposed argument to explain the improved performance of the eight-point algorithm that results from using normalized
data (Chojnacki, W., et al. in IEEE Trans. Pattern Anal. Mach. Intell. 25(9):1172–1177, 2003) relies upon adoption of a certain model for statistical data distribution. Under this model, the cost function that underlies
the algorithm operating on the normalized data is statistically more advantageous than the cost function that underpins the
algorithm using unnormalized data. Here we extend this explanation by introducing a more refined, structured model for data
distribution. Under the extended model, the normalized eight-point algorithm turns out to be approximately consistent in a
statistical sense. The proposed extension provides a link between the existing statistical rationalization of the normalized
eight-point algorithm and the approach of Mühlich and Mester for enhancing total least squares estimation methods via equilibration.
The paper forms part of a wider effort to rationalize and interrelate foundational methods in vision parameter estimation. 相似文献
104.
An increasing number of connectionist models have been proposed to explain behavioral deficits in developmental disorders. These simulations motivate serious consideration of the theoretical implications of the claim that a developmental disorder fits within the parameter space of a particular computational model of normal development. The authors examine these issues in depth with respect to a series of new simulations investigating past-tense formation in Williams syndrome. This syndrome and the past-tense domain are highly relevant because both have been used to make strong theoretical claims about the processes underlying normal language acquisition. The authors conclude that computational models have great potential to advance psychologists' understanding of developmental deficits because they focus on the developmental process itself as a pivotal causal factor in producing atypical phenotypic outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
105.
Schmitt Neal; Oswald Fred L.; Kim Brian H.; Gillespie Michael A.; Ramsay Lauren J.; Yoo Tae-Yong 《Canadian Metallurgical Quarterly》2003,88(6):979
The current study investigated the impact of requiring respondents to elaborate on their answers to a biodata measure on mean scores, the validity of the biodata item composites, subgroup mean differences, and correlations with social desirability. Results of this study indicate that elaborated responses result in scores that are much lower than nonelaborated responses to the same items by an independent sample. Despite the lower mean score on elaborated items, it does not appear that elaboration affects the size of the correlation between social desirability and responses to biodata items or that it affects criterion-related validity or subgroup mean differences in a practically significant way. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
106.
The paper deals with a physical model for the calculation of the strip temperature in a hot rolling mill. Beside the heat transfer from the strip to the environment in the different mill sections a sub‐model for the material properties of steel including phase transitions is introduced. For the application in a process automation system an online adaptation of the model to the current state of the mill is indispensable. The adaptation is explained in detail. 相似文献
107.
Drew Michael R.; Yang Cynthia; Ohyama Tatsuya; Balsam Peter D. 《Canadian Metallurgical Quarterly》2004,30(3):163
Three experiments investigated the effects of varying the conditioned stimulus (CS) duration between training and extinction. Ring doves (Streptopelia risoria) were autoshaped on a fixed CS-unconditioned stimulus (US) interval and extinguished with CS presentations that were longer, shorter, or the same as the training duration. During a subsequent test session, the training CS duration was reintroduced. Results suggest that the cessation of responding during an extinction session is controlled by generalization of excitation between the training and extinction CSs and by the number of nonreinforced CS presentations. Transfer of extinction to the training CS is controlled by the similarity between the extinction and training CSs. Extinction learning is temporally specific. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
108.
109.
David Haussler Michael Kearns Nick LittlestoneManfred K. Warmuth 《Information and Computation》1991,95(2)
In this paper we consider several variants of Valiant's learnability model that have appeared in the literature. We give conditions under which these models are equivalent in terms of the polynomially learnable concept classes they define. These equivalences allow comparisons of most of the existing theorems in Valiant-style learnability and show that several simplifying assumptions on polynomial learning algorithms can be made without loss of generality. We also give a useful reduction of learning problems to the problem of finding consistent hypotheses, and give comparisons and equivalences between Valiant's model and the prediction learning models of Haussler, Littlestone, and Warmuth (in “29th Annual IEEE Symposium on Foundations of Computer Science,” 1988). 相似文献
110.
MD Goldberg JR Canvin P Freestone C Andersen D Laoudj PH Williams IB Holland V Norris 《Canadian Metallurgical Quarterly》1997,79(6):315-322
In the bacterium Escherichia coli, H-NS-(H1, H1a) is a heat-stable protein with a molecular mass of 15.5 kDa involved in nucleoid organisation and gene regulation linked to certain signal transduction pathways. We have shown that, following addition of preparations of everted inner membrane vesicles, heat-stable cleavage products of approximately 10 kDa of H-NS are formed in vitro from newly synthesised, radio-labelled H-NS and from purified H-NS. The 15.5 kDa protein and its cleavage products were also recovered from a minicell system. These results raised the possibility that cleavage of H-NS is physiologically significant. However, the cleavage of H-NS observed appears to occur during cell breakage and to depend on the method of protein extraction and the presence of the outer membrane protease, OmpT. Nevertheless, the results indicate that H-NS may contain at least two separate domains with cleavage occurring between these domains at a preferred OmpT site. Failure to take account of H-NS cleavage in sample preparation and analysis can lead to serious underestimation of H-NS levels. 相似文献